This disclosure is directed to a bumpless constant rate pumping system. Constant rate pumps are often required in many circumstances. For instance, in a refining process, it may be necessary to inject a minute quantity of a trace constituent into a vessel against a wide range of back pressures including low to high pressures. The apparatus of the present disclosure is directed to a pump which provides such an output, namely, a constant rate of flow which is pumped at a specified pressure without bumps or pulsations in the flow rate dependent on the type of the connective tubing.
There have been attempts in the past to provide various and sundry constant rate systems. The apparatus of this disclosure is apt to be an improvement over them. The apparatus is an improvement in the sense that it provides a rate of flow which is constant. The rate of flow is maintained steady and free of pulsations or bumps dependent on system materials. For example, flexible plastic tubing can be used but it yields to pressure and hence serves as a somewhat inferior material to metal tubing. Metal conduit is, however, more costly and is used only when the performance required demands the expense. Heretofore, multicylinder pumping mechanisms have found favor. They ordinarily, however, have difficulty in achieving a switchover where the flow is coming from a first cylinder and thereafter additional cylinders in the apparatus. The switch-over from a first to a subsequent cylinder has heretofore entailed a periodic bump or surge. These have occurred during pressure build up and drop in the manifold which is common to the several cylinders. Bumps or surges in some circumstances cannot be tolerated. Accordingly, the apparatus of the present invention has overcome this handicap by the provision of a pumping system which is free of bumps and surges when the multiple cylinders cycle in and out of operation.
The present apparatus overcomes these problems. The pumping apparatus disclosed herein is able to pump a fluid at a constant rate from a multicylinder apparatus where the pressure is free of pulses or surges. The apparatus switches from one cylinder to the other in a bumpless fashion.